On Mon, 28 Nov 2016 10:34:08 -0700, "Bob La Londe"
wrote:

Well, I just had my first failure with my PM 1440. The cam-lock on the
tailstock broke. This lathe has been just so amazing compared to my other
Chinese lathes that I got my feelings hurt. LOL.

It wasn't a particulary hard fix. I had to pull and split the tailstock to
remove the shaft, cam, and pull block. I found the cam was held to the
shaft with a spring pin (or roll pin if you prefer). It had broken. I know
why it had broken. Spring pins are strong, but not as strong as you might
think. When ever I do some heavier drilling (like clear a hole with a 1"
drill bit) I tend to bump the handle firmly with my hand. That cumulative
force surely is what caused the pin to break.

The other issues is the pin is in my opinion a little short for the job. I
think its a standard length pin though as I had several the same length in a
box of assorted spring pins I bought a while back for emergencies. I think
as a result the shorter than full depth engagement in the cam allows it to
flex more when I bump the handle. Since I had a pin and I was in the middle
of a project I put it back together and dialed the tailstock back in. I may
find it hard to break the habit of bumping the handle so eventually I am
sure it will fail again. When it does I would like to be ready with a
better solution. My first thought was to use a solid stainless dowel cut to
length. Throw some Loctite on it and call it a day. Drilling and reaming
for a nice light interferrence fit might be tedious, but its within my
capability. Just a few tenths so it stays in place, but can be driven out
easily enough. If the fit is to both parts, the cam and the shaft, there
shouldn't be any slop to allow the pin to cause wear. Are there any
issues with that? The other thought I had was to make a new cam that has to
be pressed onto the shaft eliminating another other possible play/wear
issue. A one piece shaft and cam is not a practical solution. I'd have to
drill out the side of the tail stock and the insert a bushing to support the
shaft. Not impossible, but a lot of unnecessary work and seriously
overkill. On the other hand it would probably outlast me. LOL.

This brings us to failure number two. After I put it back together I threw
a piece of stock in the chuck and turned a point to align the tailstock to.
Then I threw a dead center in the tail stock and started lining up the
points. When I got out my loupe I found the center was blunt. Looked like
maybe it was dropped. I couldn't see it with just my glasses on, but it was
clear to see with the loupe. Thinking maybe I dropped it and didn't
remember I got one out of the tool cart that had never been used before. It
was also blunt. It was a nice tiny dome, but it was blunt. Orders of
magnitude bigger than the tip on my turned point. Atleast it seemed uniform
so I dialed it in as best I could. I realize even with hardened and ground
steel handling is coming to take off needle tips from an object that heavy,
so maybe that's the norm. I don't know. Both centers came with the lathe so
perhaps they are just lower grade Chinese parts. Do all dead centers have a
domed tip when looked at under a glass?


If you are worried that the tail stock center doesn't come to a sharp
point just grind it.

Back in the days of turning between centers it was a common job for
apprentices. Make sure that both the headstock and center were clean
and had no burrs, install the tail stock center in the head stock and
re-grind it with the tool post grinder. Usually both centers were
ground at the same time.